1. Field of the Invention
The invention generally relates to hydraulic and earth engineering and more specifically to shoring, bracing, or cave-in protection for foundations, especially trench shoring of the shield type.
2. Description of the Related Art
In the art of trench shoring, U.S. Pat. No. 3,159,978 to De Lillo discloses a sheathing system in which slat-like shields are telescoped to cover the walls of a trench at selectable depth. The shields are suspended from cross beams that are transverse to the trench and carry longitudinal bridging beams whose width can be adjusted on the cross beams. This shoring system is not mobile and requires a crane to lift its components from the trench.
U.S. Pat. No. 3,541,799 to Jost et al discloses a shoring system in which rails are placed on either side of a ditch, and a car rolls on the rails. The car supports bracing walls that are of endless design and are free to roll over the ditch walls as the car progresses. The car is pulled by a separate tractor, and this pulling, in turn, causes the bracing walls to roll over the ditch walls.
U.S. Pat. No. 3,820,345 to Brecht discloses a self-propelled shoring machine in which the rear wall is composed of pushing members that advence the machine in the trench by pushing against the fill dirt behind the machine. The pushing members also can compact the fill dirt when the side, shoring plates are hydraulically spread to hold the machine in a fixed location. A conveyor carries dirt from the front to the rear. It is proposed that this machine rides on wheels against the bottom of the trench, which can be impractical. This shoring machine must be installed and removed by separate means, such as a crane, and it is evident that the side plates cannot be easily raised or lowered to fit the requirements of each particular trench.
U.S. Pat. No. 4,002,035 to Wright discloses a mobile frame that can carry a plurality of vertically slidable shoring plates. The frame is mounted on tracks or wheels, and the sides of the frame and wheels can be separated to accommodate different width trenches. The shoring plates are separated by hydraulic cylinders.
U.S. Pat. No. 4,421,440 to Scheeplers discloses a shoring system in which several plates are located one above the other, and the system comtemplates a removal technique in which the lower plates is withdrawn toward the center of the trench and then raised.
U.S. Pat. No. 4,521,137 to Brecht discloses a moveable shoring system in which upper and lower sections of a framework move longitudinally so as to push the framework forward by pressure against the backfill.
It would be desirable to have a device for shoring trench walls and thereby improving the safety of personnel in the vocation of laying pipe and performing other installations in trenches, wherein such device is both safe and inexpensive so as to be widely available.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the trench shoring machine of this invention may comprise the following.